/**
 * 名称： 认识变量
 */

void setup() {
    // put your setup code here, to run once:
    pinMode(13, OUTPUT);
}

void loop() {
    int delayTime = 3000;       //3秒, 如不初始化，默认为0
    // put your main code here, to run repeatedly:
    digitalWrite(13, HIGH);     //turn the LED on
    delay(delayTime);                // wait 3s
    digitalWrite(13, LOW);      //turn the led off
    delay(delayTime);                //wait 3s
}
